Room-temperature molten salt electrolytes for photoelectrochemical solar cells

In 1991, Gratzel and co-workers published promising results from dye-sensitized, nanocryst., photoelectrochem. solar cells (DNSCs), with huge internal surface areas. A Gratzel cell consists of a dye-sensitized TiO2-electrode, a platinized counter electrode and an electrolyte contg. a redox pair of iodide/triiodide ions. Room-temp. molten salts have qualities, such as high cond., ionic mobility, thermal stability and negligibly volatility, which make them suitable as electrolytes for solar cells. Two systems of potential electrolytes have been successfully synthesized and analyzed, based on the redox pair I-/I3- using different cations: 1. trialkylsulfonium iodides, (R2R'S)I 2. trialkylsulfonium iodides with addn. of metal iodides The capability to act as electrolytes in DNSCs was investigated by measuring the overall light-to-elec. energy conversion efficiency in 100-1000 W/m2 illumination (AM 1.5) using a solar simulator, and also the incident monochromatic photon-to-current conversion efficiency (IPCE). Results showed that liq., iodine-doped trialkylsulfonium iodide-salts work very well as electrolytes in DNSCs.